Variable flow pump



Feb E951 c. E. GRAY VARIABLE FLow PUMP CHAQLES B. GRAY A-H'orne C. B. GRAY VARIABLE FLOW PUMP Feb. 6, 1951 7 Sheets-Sheet 2 Filed June 13, 1947 w ma uv m We IS A /I mm y//w/ um ON mm .M |||I|L|I| Ii... IIILH. 1.1. I 1, l ihm x v :sieswwi? f y man m mw# m. o. Se V SQ@ m Y .u r Y .mm lglllllllll rm 1| .l l i ...N n... um f\\ Y 4 mm N.. Q@ .Gm n f `m H mw. n \,\o0 mm-/.m mw 4 ,l m@ wm n@ 2. i S s wir im Feb. 69 195i c. B. GRAY 2,540,328

VARIABLE FLOW PUNP Filed June 13, 1947 7 Sheets-Sheet 3 ENTUR.

CHARLES B. GRAY i A avm/Q Feb.. 6, i951 Filed June 13, .1947

c; a. GRAY VARIABLE FLOW PUMP 7 Sheets-Sheet 4 Feb. 6, 1951 C. B. GRAY VARIABLE FLOW PUMP 7 Sheets-Sheet 5 Filed June 13, 1947 aan a3 A-Hor w29 Feb. 6, 1951 c. B. GRAY VARIABLE FLow Pura? 7 Sheets-Sheet 6 Filed June 13, 194'? INVENTOR. enanas GRAY A-H'crney Feb. 6, 1951 c. B. GRAY 2,540,328

VARIABLE FLOW PUMP Filed June 13,'1947 '7 Sheets-Sheet 7 INVENTOR. QHARLES B. @RAY BypfW//Mw/ Patented Feb. 6, 1951 UNITED STATES PATENT OFFICE 7 Claims. l

This invention relates generally to fluid-pressure power mechanisms and more particularly to an improved construction of a fluid pressure pump having a plurality of reciprocating pistons, the displacement of which may be varied from zero to full stroke to vary the capacity of the pump without changing the speed of the prime mover for the pump.

Among the |principal objects of the present invention is to provide a variable displacement pump of simple construction in which the pressure fluid is displaced by rectilinearly movable piston elements operating sequentially, the design, construction and operation of the pump being generally such as to provide for a high power-to-weight ratio, high efiiciency and an ability to respond readily to high and rapid accelerations as required of the developed fluid pressure.

Still another object of the present invention is to provide a multiple piston type of variable capacity pump wherein the necessity for extremely close clearances and tolerances between the moving parts thereof to prevent leakage of the high pressure fluid is obviated; which is suitable for use with either oil or water as the fluid medium; and which is capable of developing working pressures unlimited in amount.

A still further object of the present invention is to provide a variable capacity recipro- -cating piston type of pump having means for limiting the fluid pressure to a preselected value as well as means automatically operative to maintain the developed pressure at its said preselected value.

Generally, it is among the objects of the present invention to provide a pump, the capacity or output of which may be readily varied at will without stopping the pump or varying the speed of its prime mover; to provide a pump which is exceedingly rugged in construction, which is capable of withstanding long periods of use at high speed and under high developed fluid pressures, and which has a minimum of moving parts, all of which are readily accessible for replacement, adjustment and repair; and to provide a pump wherein frictional and other resistances, so characteristic of the radial type of variable capacity pump, are reduced to a pracl 'ticauy negubie minimum.

Still other objects and advantages of the invention will appear more fully hereinafter,- it being understood that the present invention consists generally in the combination, construction, location and general arrangement of parts, all

as will appear more fully hereinafter, as shown in the accompanying drawings and as finally pointed out in the appended claims. l

In the said accompanying drawings, which are illustrative of a preferred embodiment of the principles of the present invention:

Figure 1 is a longitudinal sectional view of a pump constructed in accordance with and embodying the principles of the present invention;

Figure 2 is a View similar to Figure 1, but showing the piston elements shifted into positions for minimum stroke thereof;

Figure 3 is a transverse sectional view taken on the line 3-3 of Figure 2;

Figure 4 is a transverse sectional view taken on the line 4-4 of Figure 2;

Figure 5 is an end elevational view of the Dump;

Figures 6 and 7 are elevational views illustrating the operation of the rotatable cam plate for successively effecting reciprocation of the piston elements;

Figure 8 is an elevational view of a modified construction of cam plate operative to effect a two-cycle reciprocation of each piston element for each revolution of the cam plate;

Figure 9 is a face view of the cam plate illustra-ted in Figure 8;

Figure 10 is a schematic View illustrating the application of the pump of the present invention for fluid pressure operation of a work utility, such as a press, a portion of the pump and its associated control valve mechanism being shown in section;

Figures 1l and 12 are side and end elevational views, respectively, of a modified construction of control valve mechanism for use in association with the pump;

Figure- 13 is an enlarged sectional view taken on the line l3`|3 of Figure 11; and

Figure 14 is a schematic view Aillustrating use of the pump in assocation with the valve control mechanism of Figures 11 to 13 for operation of a work utility.

Referring now to the drawings and more particularly to Figures 1 to 9 thereof, it will be observed that the pump of the present invention essentially consists of a stationary main body member I 0 of generally circular form suitably supported upon a foundation or base Il. vExtending axially through the center of the body member I0 is a rotatable shaft I2, one end of which is fitted with a drive pulley I3 which is suitably belt-connected to a constant speed afferisce prime mover, such as an electric motor (not shown) for operating the pump.

Securd to the main body member I in axially spaced relation with respect thereto is an end plate I4 having a central hub I5 in axial alinement with the central bore of the body member IB, this hub being adapted to receive therein the freely projecting end of the drive shaft I2. Preferably, the end plate I4 is fixed in its axially spaced relation relatively to the body member I by means of an intervening sleeve I6, the opposite endsof which are respectively secured tothe proximate ends of the body member I0 and the end plate I4 by the circumferentially spaced bolts I1I1. The intervening sleeves I5 constitutes in eiect'the cylindrical wall of a chamber I8 formed between the proximate ends of the main body member I0 and its axially spaced end plate I4.

Keyed to the drive shaft I2, as by the pin I9, for rotation Within the enclosed space I8 is a cam plate 20. Interposed between the rotatable cam plate and the relatively stationary end plate I4 are suitable end thrust bearings 2 I, which provide for free rotation of the cam plate and the drive shaft I2 relatively to the end plate I4 at the same time that the latter serves as an axially fixed backing for the cam plate. As most clearly appears in Figures l, 2, 6 and '1, the cam plate 20 vis marginally provided with a circum' ferentially continuous cam track 22 which rises gradually through an arc of 180 degrees to a high point 23 and then drops gradually through the remaining arc of 180 degrees to the low point 24. The form of this cam track may be varied as desired and instead of providing it with a single high point as in Figures 6 and '7, it may be provided with a pair of diametrically opposed high points 25-25, each spaced 90 degrees from the diametrically opposed low points 26-26 oi the cam track. The function of this rotatable cam plate will presently appear.

Slidably mounted within the stationary main body I0 of the pump are a plurality of circumferetnially spaced piston elements 21, each of the form most clearly shown in Figures 1, 2, 1I) and 14. As shown in these figures, each of these piston elements 21 is provided with a main body portion 30 having a coaxial stem 3| of reduced diameter, which latter in turn is provided with a coaxial terminal end 32 of still further reduced diameter. The outer ends of the main body portion 30 of the piston elements are each cut away as at 33 to provide a flat face 34 against which is rotatably mounted a roller 35. These rollers 35, each of which is journalled upon a pin 36 extending diametrically through the cutaway end portion 'of the piston element and at right angles to the iiat face 34 thereof, are of diameters somewhat less than the diameters of the body portions 30 of the piston element (as shown in Figure 3), in view of which these rollers 35 do not interfere with reciprocal movement of the piston elements axially of the stationary main body member I0.

It will be observed that the several piston elements 21 are so relatively arranged circumferentially about the drive shaft I2; as to present the several rollers 35 thereof in contact with the cam track 22, To this end, the several rollers 35 are circumferentially spaced about a circle the diameter of which is substantially equal to that of the circular cam track 22. In consequence of this arrangement of the rollers 35 relatively to the cam track 22, it will be apparent that as the track operating against the several rollers 35 causes the same to be successively shifted axially away from the main body of the cam plate and so eiect movement of the piston elements 21 successively toward the drive pulley end of the stationary main body member I0.

As most clearly appears in Figures 1 and 2, the piston elements 21 are respectively disposed with- 1n circumferentially spaced bores formed in the main body member I0, these bores being arranged with their axes extending in parallel relation to each other and to the longitudinal axis of the drive shaft' I2. Each of these bores is provided with a relatively large diameter section 38 for receiving the body portion 30 of the piston element and with a reduced diameter section 39 for receiving the reduced diameter stem 3| of the piston element. The sections 39 of the circumferentially spaced axial extending bores respec-V a cylindrical sleeve 40 which closely ts the reciprocating piston 3i, this sleeve 4l) being removably secured in position by a plug 4I in threaded association with a removable thimble 42. Suitable packing glands or washers 43-44 are provided at opposite ends of the piston sleeve 40, while similar packing glands or washers 45 are disposed at the inner end of the thimble 42, the Whole providing a fluid-tight cylinder for the reciprocating piston 3I. Each of the cylinders 39 is provided with an inlet port 46 and an outlet port 41, these ports being respectively in communication witha pair of fluid conduits 48 and 49. It will be understood that a pair of such conduits 48 and 49 is provided for each of the cylin- -ders 39.

Embracing each piston 3l along the portion thereof disposed within the larger diameter section 31 of the piston bore is a coiled compression spring 5I), which operates to present the cam roller 35 of each piston element 21 in positive rolling engagement with the cam track 22 of the revoluble cam plate 2li when said piston element is in position to be actuated by the cam plate. In order to prevent any tendency of the piston elements 21 to rotate about their axes and to insure that the rollers 35 thereof are constantly in proper position for engagement by the cam track 22, a key 28 or the like is provided for each piston element, as shown in Figures 1 and 2, the inner end of the key projecting freely into a key-way 29 extending longitudinally along the piston element, thus permitting reciprocatory movement of the latter while restraining it against angular displacement.

It will be apparent from the foregoing that as the cam plate 20 rotates, its cam track 22 will cause the several piston elements 21 to be successively shifted toward the outer closed ends of the iluid pressure cylinders 39 to compress the fluid therein and force the same outwardly by way of the outlet ports 41 into and through the conduit 49 in communication with said outlet ports. The coiled compression springs 50 operate to retract the pistons when the cam rollers 35 thereof are presented in engagement with the return slope portion of the cam track 22, it being apparent that on the return strokes of the pistons 3I the pressure fluid is drawn into the piston cylinders 39 by way of the conduits 48 in communication with the fluid inlet ports 46.

By use of a rotatable cam plate of the type cam plate 20 revolves with the shaft I2 the cani u shown more particularly in Figures 1, 2, 4, 6 and '7, wherein the cam track is provided with a single high point spaced 180 degrees from its single low point, each piston completes one cycle of operation for each revolution of the cam plate. In other words, for each revolution of the cam plate each piston partakes of a single forward and a single return stroke. By providing the cam plate with a cam track having a pair of circumferentially spaced high points, as in the form of cam plate shown in Figures 8 and 9, the several pistons each complete two cycles of oper-ation for each revolution of the cam plate.

It will be understood, of course, that the strokes of the several pistons .operating successively by engagement of the rotatable cam track against the several cam rollers 35 of the pistons are of uniform length or magnitude. In order to vary such length of magnitude of the strokes of the several pistons, the pump of the present invention includes a fluid pressure operated mechanism for shifting the several piston elements relatively to the rotating cam plate 20.

This mechanism, as most clearly appears in Figures l and 2, includes an axially shiftable annulus 5I suitably disposed within the enclosed chamber I8 housing the rotatable cam plate 20. This annulus 5I is supported upon the end plate I4 for axial movement relatively to the rotatable cam plate 20 by means of a plurality of circumferentially spaced plunger elements 52, which respectively extends through the said end plate I4 and into uid pressure cylinders'53 suitably secured, as at 54, to the end plate.

The outer ends of' these fluid pressure cylinders 53 are respectively provided with ports 55 in com- Y munication with a pressure fluid conduit 56, the

arrangement being such that upon the supply of fluid under pressure by way of said conduit 56 into the several cylinders 53, the plungers 52 will be -actuated to shift the annulus 5I axially of the rotating cam plate 20, said axial shifting of the annulus 5I being, of course, resisted by the coiled compression springs 50. Depending upon the pressure of the fluid exerted against the plungers 52 of the cylinders 53, the extent to which the annulus 5I is shifted may be controlled as desired to thereby vary the magnitude of stroke of the pistons 3I within their respective cylinders 39.

This Variation in magnitude of stroke of the pistons as effected by change in position of the annulus 5I is apparent upon comparison of Figures l and 2. In Figure l, it will be observed that the annulus 5I is in such position as to permit the cam plate 20 to effect successive reciprocation of the pistons 3| for maximum stroke thereof, each piston being shifted through a length or magnitude of stroke equal to the axial distance between the low point 24 and the high point 23 of the cam track 22. When, however, the annulus 5I is axially shifted into its position shown in Figure 2, the cam track 22 of the rotating cam plate is no longer effective to impart reciprocation to the several pistons and the latter simply remain relatively stationary during rotation of the cam plate. For any intermediate position of the annulus 5I the length and magnitude of stroke of the several pistons is correspondingly adjusted, the pistons being successively shifted on their pressure stroke only as the cam rollers thereof are successively presented in'contact with the rising portion of the rotating cam track 22.

Figure 10 illustrates more or less schematically an application of the pump of the present invention in a system for hydraulically operating a press, although it will be understood that this pump is equally applicable for use in theA operation of all kinds of hydraulic machinery, in connection with which it is designed to produce a moving or holding force of unlimited magnitude for use in pressing, forming, extruding, drawing or forging operations on metals and other compositions, in shifting or moving heavy loads as in lift tables, elevators and the like, and in other fields wherein it is desired to employ a uid under uniformly constant high pressure. As illustrated in Figure 2, the several inlet conduits 48 leading into the several cylinders 39 are connected to a common conduit or manifold 51, while the several conduits 49 leading from the cylinders 39 are commonly connected to a single conduit or manifold 58.

Referring now again to Figure 10, it will be observed that the pump mechanism of the present invention is operative to pump the pressure .fluid into the manifold conduit 58 at a rate suihcient to maintain therein a preselected operating pressure for the fluid, the existing pressure in this manifold 58 being visually determined by suitable pressure gage (not shown) High pressure fluid is delivered from the manifold 58 to the uid pressure operating cylinder 59 of a work utility, such as a hydraulic press, through a three-way valve 69, in one position of which, as shown by the full lines in Figure l0, the fluid under pressure is directed by way of the conduit 6I into the lower end of the cylinder 59 for raising the piston 6I)a thereof. When it is desired to lower the press under fluid pressure, the valve 60 is set as shown in the dotted line insert in Figure 10 to direct the fluid into the upper end of the cylinder 59 by way of the conduit 62.

The fluid which is forced into the lower end of the press cylinder 59 forces the piston ISI)a upwardly and so causes the fluid confined in the upper portion of the cylinder 59 outwardly thereof by Way of the conduit 63 and through the threeway valve 64 and the conduit 65 into the oil reservoir 66, For this operation of the press, the valve 64 is set as indicated by full lines in Figure 10.

Conversely, when the valve 60 is set as indicated by ts dotted line representation to direct the pressure fluid into the top of the cylinder 59 and so force the piston 6|]a downwardly, the fluid confined in the lower end of the cylinder is forced outwardly therefrom by way of the conduit B'I through the valve 64 and the conduit 65 into the oil reservoir 65, the valve 64 being then set in the position as indicated by its dotted line representation in Figure 10.

The fluid to be compressed by the pump is, of course, drawn into it from the oil reservoir 63 by way of the conduit `li8,which is in communication with the pump intake manifold 51. To insure unidirectional flow of the pressure fluid through the pump, the several intake conduits 48 leading to the piston cylinders 39 are provided with check valves 69, while the several outlet conduits 49 leading from the said piston cylinders are similarly provided with individual check valves 10. Any suitable manual or automatic means (not shown) may be employed for simultaneously operating the valves 60 and 64 for controlling proper circulation of the fluid to and from the fluid pressure operating cylinder 59 of the work utility.

In order to develop and maintain a predeterminedly fixed operating pressure for actuation of the work utility, a valve mechanism oi the audace construction shown in Figure may be included in the system, this mechanism being operative to supply fluid under pressure to the fluid pressure actuated plungers 52 for axially shifting the annulus 5I automatically into adjusted position for controlling the extent or magnitude of the operating stroke of the pump pistons 3l. As clearly appears in Figure 10, this valve mechanism essentially comprises a pair of axially spaced members 1I and 12 secured together in axial alinement by an intervening sleeve 13, the opposite ends of this sleeve being respectively secured to the members 1| and 12 by the bolts 14-14. The member 1| is provided with an internal cavity having a lateral port 15 in communication with the manifold 55 by way of a conduit 11. The outer end of said member 1I is axially bored as at 18 for reception of an axially adjustable stem 19, the axial adjustment of this stem being effected by means of a nut 88 threadedly secured as at 8i to the outer end of the member 1i.

The opposite end of said member 1| is centrally bored as at 82 for receiving the inner end of a fluid pressure actuated plunger 83, the major p0rtion of which is disposed yfor axial movement within a. fluid pressure cylinder `8l formed internally of the member 12. This cylinder 84 is provided with a lateral port 85 in communication, by way of the conduit86, with the high pressure manifold 58 of the pump mechanism. 'Ilhe fluid pressure operated plunger -83 is provided 'at its outer end with a pilot stem v88, the plunger being maintained in axial alinement with the axially adjustable stem 19.

A coiled compression spring 81 is interposed between proximate ends of the stem 19 and the plunger 83, tending normally to shift the plunger against the force exerted by the high pressure fluid delivered to the cylinder 84 by way of the conduit 86. As shown in Figure 10, suitable packing glands are provided to prevent loss of fluid pressure from within the chamber 15 of the member 1| yand from Within the cylinder 84 of the member 12. The end of the plunger 83 which projects interiorly of the chamber 15 operates as a piston to compress and force fluid contained within the chamber 15 under pressure through the conduit 11 to the fluid pressure cylinders for the plungers 52. It will be observed that the chamber 15, the conduit 11 and the fluid pressure cylinders 53 constitute in effect an oil system having opposite closed ends, this system being normally filled with a uniform supply of oil so as to provide an oil column which courses back and forth within the conduit 11 accordingly as the plunger 83 is axially shifted under the force of the high pressure fluid delivered to its operating cylinder 84.

In normal operation of the system as shown in Figure l0, it will be understood, of course, that the rotative speed of the main drive shaft I2 of the pump is maintained constant and that each piston 3l of the pump completes one or more full cycles of reciprocation for each revolution of the drive shaft, the number of reciprocating cycles of operation of each piston per revolution of the drive shaft being dependent upon the form of cam plate employed as hereinbefore described. The extent or magnitude of the stroke of each piston is, however, dependent upon the relative position which is assumed by the axially shiftable annulus 5I, it being apparent that as said annulus is shifted away from the end plate I4 of the pump, the magnitude of the pump stroke is correspondingly reduced. When this annulus 5I, is

shifted into its position shown in Figure 2, the pump stroke is reduced to zero by virtue of the fact that the rotating cam plate 20 is ineffective to cause reciprocation of the piston elements of thepump.

Assuming that it is desired to establish and maintain an operating fluid pressure, of say 5000 pounds, for delivery to the fluid pressure operating cylinder of a work utility, such as, for example, the cylinder 58 shown in Figure 10, all that is necessary is to start the pump working by imparting rotation to the drive shaft i2 thereof by means of its prime mover (as shown). With the parts of the pump arranged as shown in Figures 1 and 10, the cam plate 20 will effect, in conjunction with the coiled compression springs 50, reciprocation of the fluid pressure cylinder pistons 3l of the pump at their full or maximum strokes. As the fluid pressure developed by the several pump pistons builds up toward the preselected value, the developed pressure will be indicated by suitable gages (not shown) included in the high pressure lines of the system, such as in the conduit 58 or in the conduct 86. In order to hold the pressure at its predeterminedly fixed value, the adjusting nut '80 on the control valve mechanism is adjusted to balance the force of the spring 81 against the opposing force of the pressure fluid delivered to the cylinder 8l by Way of the conduit so as to adjust the plunger 83 in such position that the fluid column in conduit 11 becomes effective to shift and hold the annulus 5I in its position shown in Figure 2, in which latter position the pump pistons remain relatively stationary.

Should the fluid pressure developed by the pump for delivery to the work utility exceed the predetermined maximum limit (e. g. 5000 pounds), the pressure of such fluid deliveredto the plunger 83 of the control valve by Way of the conduit 86 would only tend to shift said plunger axially against the compression spring 81 with the result that the fluid column in the conduit 11 would continue effective to hold the annulus 5I in its position shown in Figure 2, in which position there would be no pumping action by the pump pistons and, therefore, the fluid pressure developed by the pump would be limited to its predetermined maximum value.

Should, however, the developed fluid pressure drop below its predetermined maximum value, the fluid under such reduced pressure delivered to the cylinder 84 by Way of the conduit 86 would .be ineffective to hold the plunger 83 balanced against the compressive force of the spring 81 and, consequently, said plunger would be forced axially toward the outer end of the cylinder 84 under the influence of the spring 81, thereby permitting the fluid column in the conduit 11 to shift in the direction reverse from that indicated by the arrows in Figure 10 under the influence of the compression springs 58 acting upon the pump piston elements 21. The annulus 5I would then tend to be returned toward its position shown in Figure 1. so as to again render the rotating cam plate 28 effective to cause successive reciprocation of the pump pistons.

It will be apparent that this cycle of operation would continue so long as the pump remained in operation, the pistons thereof being operative whenever fluid pressure developed by the pump drops below its predetermined maximum value to establish and maintain the fluid pressure at said value.

Should it be desired to maintain a higher or 9 lower iiuid pressure than that mentioned hereinbcfore, then the adjusting nut 80 of the control valve mechanism is manipulated to correspondingly adjust the compressive effort o! the spring 81 against the fluid pressure actuated plunger 83. For a reduced maximum fluid pressure, a smaller eiort would be required to be exerted by the plunger to overcome the force of the spring 81, while for increased maximum pressure, a greater effort would be required for over- 10 coming the compressive force of the spring 81.

In this connection, it will be noted that the end of the plunger 83 which is immediately subject to the pressure fluid delivered to the cylinder 94 by way of the conduit 85 is reduced in 15 its effective cross-sectional area by the pilot stem 88. By so reducing the effective crosssectional area of the plunger at the end thereof which is acted upon by the pressure uid, the

coiled compression spring 81 operative against 20 the opposite end of the plunger 03 may be materially reduced in strength without aiecting proper operation of the control valve mechanism.

Figures l1 to 13, inclusive, illustrate a modied application of the pump wherein a combination check and relief valve mechanism, designated generally by the reference numeral 90, is employed for maintaining the pressure developed by the pump at the desired level. By use of this relief valve mechanism, as shown more 3 particularly in Figures 11, l2 and 13, it becomes unnecessary to employ in the pump the axially adjustable annulus 5| illustrated in Figures l, 2 and and the parts immediately associated with said annulus. In all other respects, however, the pump as employed in the arrangement* of Figures ll to 14 is similar to that hereinbefore described. n

Referring now more particularly to Figures l1 and 12, it will be observed that the mechanism 90 includes a main body member 9| in the upper portion of which is mounted an oscillatable Valve cock 92 having a single duct 93 the inner end of which is adapted to be brought into registry with one or the other of a pair of discharge ducts 94 0 justing the hand wheel |23 upon and 95 extending upwardly through the top of 4 the stationary body member 9|. As shown in Figure 12, these ducts 94 and 95 are respectively in communication with conduits 96 and 91 leading to opposite sides of a double acting iluid pressure cylinder 58 (see Figure 14) for operat- 60 ing any desired work utility.

The oscillatable valve cock 92 is suitably actuated by an operating handle 99 which may be manually or automatically controlled for reversing the direction of flow of the high pressure 5 uid to the Work utility operating cylinder 98. The body member SI is provided with an inlet passage |00 having a pair of spaced discharge openings |t| and |02 with which the duct 93 of the oscillatable cock 92 may be selectively brought into registry, so as to selectively connect the opening l 0| with the discharge duct 54 or the opening |02 with the discharge duct 95, the inlet passage |00 being in communication with a conduit |03 leading from the high pressure discharge manifold of the pump.

Provided in the base or lower part of the stationary body member 9| of the mechanism 90 is a fluid pressure operated piston being of single acting type and being reciprocable within a cylindrical bore |05 having a removable end plug |06. Preferably, this end plug is provided with a vent |01 for venting the interior'of the cylinder |05 at the outer end of the piston 0 the inlet ports 46 of the |04, this piston 70 l0 to atmosphere. 'l'ne opposite end of the cylinder is provided with a lateral port |08 which is in free communication with the high pressure conduit |03 by way of a conduit |09.

The operating stem or rod ||0 for the piston |04 extends outwardly of the member 9| through a suitable stuffing box arrangement and axially through a relief valve unit designated generally by the reference numeral ||2. This latter unit includes a valve body |3 having an inlet port ||4 and a discharge port H5. These ports ||4 and 5 are in communication with each other by way of internal passages IIS and ||1 formed in the body ||3, these internal pas sages including an axially bored valve member I8 having a conical valve seat ||9.

The operating stem ||0 for the piston |04 extends axially through th'e unit ||3 and is provided at a suitable point in the length-thereof with a valve closure element I shaped com-v plementally to the valve seat ||9 for seating engagement therewith to normally close oi the communicating passages between the inlet port ||4 and the discharge port ||5. The portions of the rod ||0 which project through the opposite ends of the unit ||3 are suitably packed as at |2| and |22 to prevent leakage of fluid from within the valve unit by way of the reciprocating stem 0, and the freely projecting end of said stem is provided with a hand wheel |23 operatively mounted upon the threaded end portion |24 of the stem I0. A coiled compression `spring |25 embraces the stem 0, as shown, and so imparts a biasing action upon the sternv I0 which tends normally to hold the valve 20 closed against its seat |'|9, this spring biasing action being assisted by the pressure of the fluid entering the inlet ||4 and directed against the exposed surface of the valve |20. By axially adthe stem 0, the compressive force of the spring |25 may be varied as desired. It will be observed that the stem ||0 serves both as a connecting rod for the piston |04 and as a stem for the valve |20 so that movement of the piston |04 under iniluence of the pressure fiuid delivered to its cylinder may unseat the valve |20 from its seat H9 whenever such fluid is of a pressure suicient to overcome the opposing bias of the spring |25 and the pressure on the valve |20.

Figure 14 illustrates use of the valve mechanism 90 in association with the pump for controlling delivery of the pressure fluid at its predeterminedly fixed pressure to the fluid pressure operating cylinder 98 of' shown). In this schematic arrangement of Figure 14, the fluid to be delivered under suitable pressure from the pump to the work utility is initially drawn from the fluid reservoir |26 to pump cylinders by way of the conduit |21, the uid under pressure developed by the pump being then delivered by Way of the conduit |03 to the inlet port |00 of the reversing valve having the rotatable cock In one position o1' this valve cock 92,y as shown in Figure 14, the high pressure iiuid is delivered by way of the conduit 91y and a threeway valve |28 into one end of the double acting fluid pressure cylinder 98, the uid contained in the opposite end of this cylinder being forced therefrom upon movement of the piston in the direction indicated by the arrow through the three-way valve |29 and the conduit |30 for re turn to the reservoir |26. The circulation of the fluid for operation of the piston of the cyla Work utility (not inder 98 in the direction indicated, that is, from right to left in Figure 14, is in the direction shown by the full line arrows.

Upon rotating the valve cock'92 into the second of its two operating positions so as to Dresent the duct 93 thereof in communicating registry between the discharge opening and the duct 94 (see Figures 12 and 14), the high pressure fluid will then be delivered in the direction indicated by the dotted line arrows of Figure 14 by way of the conduit 96 and the three-way valve |29 to the left hand end of the cylinder 98, while the fluid contained in the opposite end of the cylinder will be forced therefrom by way of the three-way valve |28 and the conduit |3I into the fluid reservoir |26. For flow of the fiuid in the direction just described, the three-way valves |28 and |29 will, of course, be adjusted into their positions shown by the dotted line inserts in Figure 14, thereby insuring unidirectional flow of the fluid to and from the cylinder 98 to effect movement of the piston thereof in the desired direction. The operation of these three-Way valves |28 and |29 may be effected simultaneously and in synchronism with the operation ofv the reversing valve cock 92 by any suitable mechanism (not shown), which latter mechanism may be manually or automatically controlled as desired.

By suitably adjusting the compressive effort of the spring |25 by means of the adjusting hand wheel |23, it will be apparent that a greater or less pull may be imparted to the stem of the relief valve mechanism to maintain the valve closure element |20 in seated engagement with its valve seat H9. Opposing this spring bias on the valve stem ||0 is the pressure of the fluid which is delivered into the cylinder by way of the conduit |09 and the port |08. Assuming that the spring |25 is adjusted for an operating iluid pressure in the system, of say 5000 pounds, it will be apparent that so long as the pressure does not exceed this value, the spring |251will Y tend constantly to maintain the valve |20 in tightly closed engagement with its valve seat I9. thus preventing any ilow of fluid through said closed valve to and out of the discharge port I |5.

However, should the iluid pressure in the system as developed by the pump exceed the predetermined maximum limit, the fluid under this excessive pressure will so operate on the piston |04 as to cause the valve element |20 to shift into open position relatively to its valve seat l I9, thus immediately opening the relief valve to passage of the fluid therefrom and into the reservoir |26 by way of the conduits |09 and |3| and, in consequence, relieving the system of the excess pressure. As soon as the iluid pressure drops to its predetermined maximum value or less, the spring |25 again becomes effective to close the valve |20 and so prevent further relief discharge of the fluid into the reservoir |26.

It will be observed that the direction of flow of the high pressure iluid for discharge relief thereof by way of the valve |20 is unidirectional and through a `by-pass system of conduits which is entirely independent of the system of conduits for circulating the fluid to and through the operating cylinder 98 of the work utility. The three-way valves |28 and |29 immediately associated with the operating cylinder 98 are, of course, operative to prevent ow of the high pressure fluid passing through the relief valve 1IIINZ1 from being delivered to said operating cyl- It will be understood, of course, that the apparatus of the present invention is susceptible of various changes and modifications which may be made from time to time without departing from the general principles or real spirit of the invention as hereinbefore set forth. For example, the number of iluid pressure cylinders employed in the pump may be varied as desired, and, in fact, a pump may be constructed in accordance with the principles of the present invention in which-only a single lluld pressure cylinder of adequate capacity is employed. It is, accordingly, intended to claim the invention broadly, as well as specifically, as indicated in the appended claims.

What is claimed as new and useful is:

1. In a iluid pressure pump, a stationary main body member, a drive shaft rotatably mounted in said body member, a plurality of fluid pressure cylinders each having a reciprocating piston spaced equidistantly about and from the axis of rotation of said drive shaft, a cam plate xed to and rotatable with said drive shaft for successively actuating said pistons, and fluid pressure operated means including an annulus embracing said cam plate and shiftable axially thereof for axially shifting said pistons relatively lto said cam plate to vary the stroke of the pistons to thereby limit the iluid pressure developed by the pump to a predetermined magnitude.

2. In a uid pressure pump, a fluid pressure cylinder having a reciprocable piston, a drive shaft for the pump, a cam plate rotatable with said drive shaft operative to engage the end of said piston to actuate the latter, and fluid pressure means including an annulus embracing said cam plate and shiftable axially thereof and operative by and in accordance with the fluid pressure developed by the pump for shifting the piston relatively to said cam plate to vary the stroke of the-piston as actuated by said cam plate.

3. In a fluid pressure pump mechanism, a plurality of fluid pressure cylinders each having its own reciprocating piston, an axially fixed rotatable cam plate operatively associated with said pistons for successively actuating the latter, a constant speed drive shaft for effecting rotation of said cam plate, and means for effecting positional adjustment of said pistons axially with respect to said cam plate to commonly and uniformly vary the stroke magnitude of the pistons actuated by said cam plate and so correspondingly vary the displacement of the pressure fluid from each of the successively actuated fluid pressure cylinders, said last-mentioned means including a fluid-pressure-operated axially shiftable annulus adapted to engage the outer ends of said pistons to limit their movement outwardly of their respective cylinders.

4. In a fluid pressure pump mechanism, a main body member, a rotatable drive shaft journalled in said body member, a plurality of fluid pressure cylinders arranged in said body member and having pistons reciprocable along axes paralleling the axis of rotation of said drive shaft, said pistons having end portions projecting freely Ifrom said body member in crcumferentially spaced relation about an end of said shaft correspondingly projecting from said body member, an axially xed cam plate rotatable with said drive shaft and operative to successively actuate said pistons, andan axially shiftable element engageable with the projecting ends of said '(5 pistons for positionally adjusting the latter relareciprocable piston, a drive shaft for the pump, an

axially xed cam plate rotatable with `the drive shaft for successively actuating said pistons, and means operative automatically to decrease the stroke magnitude of the pistons actuated by the cam plate correspondingly as the developed fluid pressure approaches a predetermined maximum value, said means including an axially shiftable element engageable with the pistons to limit their axial movement in one direction and a fluid pressure motor mechanism actuated bythe pressure uid discharged from the pump for effecting positional adjustment of said axially shiftable element relatively to said axially xed cam plate.

6. In a uid pressure pump mechanism of the character dened in claim 5 wherein said fluid pressure motor mechanism includes a uid pressure actuated plunger operative upon a closed column of uid to shift said column in accordance with axial shifting of said plunger and counterbiasing means tending to oppose shifting of the plunger under influence of the iluid pressure developed by the pump.

7. .In a. fluid pressure pump mechanism of the character defined in claim 5 wherein said fluid pressure motor mechanism includes a iluid pressure actuated plunger operative upon a closed column of uid to shift said column in accordance with axial shifting of said plunger and counterbiasing means tending to oppose shifting of the plunger under influence of the fluid pressure developed by the pump, said counter-biasing means being in the form of a compression spring having provision for varying the compressive eiort `thereof against said duid-pressure actuated plunger.

CHARLES B. GRAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,099,229 Woerner June9, 1914 1,576,445 Mitchell Mar. 9, 1926 1,603,228 Woerner Oct. 12, 1926 1,669,976 De Leeuw May 15, 1928 1,731,145 MacMillin Oct. 8, 1929 1,933,081 Stephan l Oct. 31, 1933 1,934,758 Temple Nov. 14, 1933 2,107,079 Mintele Feb. 1, 1938 2,123,815 Tweddell July 12, 1938 2,283,242 Van der Walt May 19, 1942 2,344,565 Scott et al Mar. 21, 1944 2,370,506 Tabb Feb. 27, 1945 

